RO Membrane performance appears to decrease prematurely


Well-known member
New Dow Filmtec 75gpd membrane initially reduces tds as expected to 3-6 from tap water of approx 150-155. Around the 4 month mark tds goes up to 10-15 (only 90% rejection rate) doesn’t make sense.

Tap water temp generally 60-70 degrees
Coralife 50gpd unit upgraded to 75gpd. Recently changed capillary for 75gpd production
RO product water about 50gal per week
Production, waste to product water 3-4 to 1
Pressure approx 65psi
Local water report DuPage County, Illinois, Lake Michigan water source, doesn’t appear to use chloramines, so I use regular carbon filter.

What do you think?


Are you flushing the membrane? I find when mine creeped up i would flush the membrane and it would start performing normally again.

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